Although you don't have to generate a new receiving address for each transaction and can continue to use the same address, it is not recommended and not how bitcoin was designed to be used..

Reusing addresses is bad for anonymity, and some argue less secure than using a new address for each transaction.
To improve your anonymity and security, it is recommended that you use a new address each time you receive a transaction.

The Bitcoin.com wallet will automatically generate a new bitcoin deposit address for you each time you receive a transaction into your wallet. Although you can still receive deposits to the address used, once you have received a transaction that particular address will no longer show when you tap on "Receive"

Every time you want to receive a new transaction just tap on receive, select the wallet you want the BCH/BTC going to and a fresh address will be displayed, there is nothing more that you need to do.